IC-NRLF 


SB    75    3fiD 


LABORATORY  MANUAL 


FOR 


SOIL  FERTILITY 


CYRIL   G.  HOPKINS 

AND 

J.  H.  PETTIT 


LIBRARY 

COLLEGE  OF 

AGRICULTURE 

Berkeley.  Cai. 


LABORATORY  MANUAL 

FOR 

SOIL  FERTILITY 


BY 
CYRIL    G.   HOPKINS 

AND 

J.  H.  PETTIT 


\ 


NOTE. — The  student  practices  described  in  this  laboratory  manual  are 
the  result  of  five  years'  experience  by  the  authors  in  conducting  classes  in 
a  course  of  study  in  soil  fertility.  With  some  modifications  the  usual 
chemical  methods  are  employed,  specific  chemical  directions  being  com- 
monly based  upon  those  adopted  by  the  Association  of  Official  Agricultural 
Chemists.  Otherwise  these  practices  were  originated  in  this  University. 

The  increasing  number  of  students  in  this  institution,  and  the  fact  that 
some  other  institutions  also  desire  to  use  our  manual,  induced  us  to  put 
it  in  printed  form. 

Suggestions  from  other  teachers  of  soil  fertility  regarding  possible  im- 
provements in  the  manual  will  be  gladly  received. 

THE  AUTHORS. 

College  of  Agriculture,  University  of  Illinois, 
Urbana,  111.,  July,  1905. 


LIST  OF  STUDENT  APPARATUS. 


2  Bunsen  burners  with  rubber  hose. 
2  Ring  stands. 
6  Rings  (3  sizes). 

1  Burette  clamp. 

2  Triangles,  pipe-stem. 

2  Erlenmeyer  flasks,  200  cc. 

2  Erlenmeyer  flasks,  300  cc. 

2  Beakers,  250  cc. 

2  Beakers,  400  cc. 

2  Beakers,  600  cc. 

2  Kjeldahl  flasks,  500  cc. 

2  Copper  flasks,  500  cc. 

1  Bottle,  2500  cc. 

2  Bottles,  1000  cc. 
2  Bottles,  500  cc. 

2  Bottles,  250  cc. 
2  Crucibles,  25  cc. 
2  Crucibles,  14  cc. 
i  Wash  bottle,  1000  cc. 

1  Funnel,  15  cm. 

2  Funnels,  10  cm. 
4  Funnels,  6  cm. 

1  Pair  crucible  tongs. 

2  Evaporating  dishes,  8  cm. 


2  Evaporating  dishes,  10  cm. 

I  Graduated  cylinder,  100  cc. 

i  Graduated  cylinder,  25  cc. 

i  Burette,  50  cc. 

i  Pipette,  25  cc. 

i  Graduated  pipette,  10  cc. 

1  Desiccator. 

2  Test  tubes. 

1  Double   condenser   with   connect- 

ing tubing. 

2  Watch  glasses. 
2  Pinch  cocks. 

i  Percolator,  500  cc. 

i  Measuring  flask,  250  cc. 

1  Bone  spoon. 

2  Safety  distillation  bulbs  with  rub- 

ber stoppers. 

1  Pair  forceps. 

2  Bottles,  400  cc.,  with  corks, 
i  Thermometer,  100°  C. 

10  Glass  battery  jars,  5  liters,  with 
i  cm.  drainage  hole  in  the  side, 
i  cm.  from  the  bottom. 

2  pieces  of  iron  gauze  with  asbestos 
center. 


3 C 5784 


PRACTICE  I. 
PREPARATION  OF  A  STANDARD  HYDROCHLORIC  ACID  SOLUTION.* 

By  the  use  of  a  hydrometer  and  specific  gravity  tables  prepare  five 
liters  or  more  of  approximately  one-half  normal  hydrochloric  acid,  using 
chemically  pure  concentrated  acid  and  ammonia-free  water. 

Standardize  by  the  silver  nitrate  method : — Place  exactly  25  cc.  (note 
temperature  of  stock  solution  when  measured  out)  of  the  acid  solution, 
measured  with  a  pipette,  in  a  300  cc.  Erlenmeyer  flask,  dilute  to  75  cc.,  add 
at  once  from  a  burette  sufficient  $%  silver  nitrate  solution  to  nearly,  but 
not  quite,  precipitate  all  the  chlorin.  Close  the  flask  with  a  clean  rubber 
stopper  and  shake  till  the  precipitate  will  settle  nearly  completely  in  a  short 
time.  Then  add  the  silver  nitrate  in  i  cc.  portions,  shaking  after  each 
addition,  until  the  precipitation  is  complete,  avoiding  more  than  I  cc.  ex- 
cess of  silver  nitrate  solution. 

Shake  until  the  silver  chlorid  settles  well,  wash  three  times  by  decanta- 
tion  (after  shaking  each  time)  using  about  100  cc.  of  water  containing  I  cc. 
concentrated  nitric  acid  per  liter  and  decanting  the  liquid  through  a  9  cm. 
filter.  Transfer  the  precipitate  to  the  filter,  dry,  transfer  the  bulk  of  the 
precipitate  to  a  watch-glass  or  crucible,  and  burn  the  paper  in  a  weighed 
crucible.  Add  2  to  5  drops  of  concentrated  nitric  acid  to  dissolve  reduced 
silver  and  then  2  to  5  drops  of  concentrated  hydrochloric  acid.  Evaporate 
to  dryness  without  spattering,  add  the  main  precipitate,  dry  to  con- 
stant weight  at  I209  to  130°,  cool  in  a  desiccator,  and  weigh. 

Record  the  weights  of  silver  chlorid  from  duplicate  25  cc.  portions  of 
the  standard  hydrochloric  acid. 


*To  be  done  by  the  instructor. 


6 

PRACTICE  2. 
PREPARATION  OF  A  STANDARD  AMMONIA  SOLUTION. 

Determine,  by  hydrometer,  the  specific  gravity  of  concentrated  am- 
monia and  calculate,  by  the  use  of  a  specific  gravity  table,  the  number  of 
cubic  centimeters  necessary  to  make  two  liters  of  approximately  one-fifth 
normal  ammonia  solution. 

Sp.  Gr , 

Grams  NH8  per  cc     

Grams  NH3  per  liter  in  normal  solution 

Grains  NH3  in  two  liters  of  1-5  normal  solution    

Cc.  of  cone.  NH3  equivalent   to g.  NH3 

Measure  out  the  required  amount  of  concentrated  ammonia,  add  dis- 
tilled water  to  make  the  total  volume  up  to  two  liters,  and  mix  thoroughly. 
Standardize  by  titrating  10  cc.  of  the  standard  hydrochloric  acid  with  the 
ammonia  solution,  using  lacmoid  as  an  indicator.  Make  three  titrations. 

(1)  10  cc.  HC1  is  equivalent  to cc.  NH3 

(2)  10  cc.  HC1  is  equivalent  to cc.  NH3 

(3)  10  cc.  HC1  is  equivalent  to cc.  NH3 

Average c.c.  NH3 

1  cc.  NH3  is  equivalent  to Mg  N. 

Give  reactions  in  first  and  second  practices,  and  explain  the  computa- 
tions involved  in  ascertaining  the  weight  of  nitrogen  in  I  cc.  of  the  stand- 
ard ammonia  solution. 


8 

PRACTICE  3. 
BLANK  DETERMINATION  OF  NITROGEN  IN  REAGENTS  USED  IN  DISTILLING. 

Place  250  cc.  of  ammonia-free  water  in  a  copper  flask,  add  10  cc.  of  con- 
centrated alkali  solution  (made  by  dissolving  1000  gm.  sodium  hydroxid 
and  25  gm.  potassium  sulfid  in  1000  cc.  water),  pouring  carefully  down  the 
side  of  the  flask,  connect  with  the  condenser,  shake  the  flask  thoroughly, 
heat  up-  slowly  and  distill  into  a  300  cc.  Erlenmeyer  flask  containing  10  cc. 
of  the  standard  hydrochloric  acid  and  about  15  cc.  ammonia-free  water. 
The  end  of  the  delivery  tube  should  dip  into  the  acid  solution.  Distill  to 
a  volume  of  200  cc.  Add  lacmoid  and  titrate  with  standard  NH.3. 

Titration  (1)  cc.  NH3 

Titration  (2) cc.  NH8 

Average  cc.  NH3 

State  correction  in  cc.  of  standard  NH3. 

Explain  all  reactions  involved,  including  the  use  of  the  indicator. 


10 

PRACTICE  4. 
PREPARATION  OF  AN  AMMONIUM  SULFATE  SOLUTION. 

Weigh  out  exactly  in  a  weighed  crucible  the  number  of  grams  of  chemi- 
cally pure  ammonium  sulfate  (assuming  the  salt  to  be  dry)  equivalent  to 
500  cc.  of  the  standard  ammonia  solution.  Dry  in  the  air  bath  at  115°  to 
120°  for  thirty  minutes,  cool  in  a  desiccator,  and  weigh.  Dissolve  in  am- 
monia-free water  in  a  250  cc.  measuring  flask.  Dilute  to  exactly  250  cc. 
Mix  well,  and  transfer  to  a  dry  250  cc.  bottle.  Label  and  keep  stoppered 
when  not  in  use. 

500  cc.  standard  NH3  contains gm.  N 

Percent  N  in  (NH4)2SO4  by  theory  is 

500  cc.  NH3  is  equivalent  to gm.  (NH4)2SO4 

Before  After 

ELeating         Heating 

Weight  of  crucible+(NH4)2SO4= 

Weight  of  crucible  = 

Weight  of  (NH4)2804  = 

Percent  dry  matter  in  salt  is 

How  much  of  the  ammonium  sulfate  will  it  be  necessary  to  weigh  out 
in  order  to  have  exactly  5  gm.  of  the  dry  salt? 


12 

PRACTICE  5. 
DETERMINATION  OF  NITROGEN  IN  AMMONIUM  SULFATE. 

Place  10  cc.  of  the  ammonium  sulfate  solution  in  a  500  cc.  copper  flask, 
add  240  cc.  ammonia-free  water  and  then  add  carefully,  by  pouring  down 
the  side  of  the  flask,  10  cc.  of  the  concentrated  alkali.  Connect  immedi- 
ately with  the  condenser,  shake  the  flask  thoroughly,  heat  slowly,  and  dis- 
till into  a  300  cc.  Erlenmeyer  flask  containing  10  cc.  of  the  standard  hydro- 
chloric acid  and  about  15  cc.  of  ammonia-free  water,  to  a  volume  of  200  cc. 
Add  lacmoid  and  titrate  the  excess  acid  with  standard  ammonia. 


Titrations  (1)  ................................  cc. 

(2)  ..................................  cc.NH3 

Average  .....................................  cc.  NH3 

Mgs.  N  in  sample  ..................................... 

Percent  N  in  dry  salt  ............................... 

The  percentage  purity  of  the  dry  salt  is  ................ 

Explain  all  reactions. 

Does  the  percentage  of  nitrogen  vary  directly  or  inversely  with  the  ti- 
tration  readings? 


14 

PRACTICE  6. 
FIXATION  OF  BASES  IN  SOILS. 

(a)  Place  a  small  bunch  of  glass  wool  in  a  percolator,  cover  with  i  cm. 
of  clean  sand,  and  add  100  gm.  of  clayey  soil.  Upon  this  carefully  pour 
250  cc.  of  dilute  ammonium  sulfate  solution  (50  cc.  of  the  solution  pre- 
pared in  Practice  4,  plus  200  cc.  of  ammonia-free  water).  When  percola- 
tion ceases,  mix  the  percolate  thoroughly  and  determine  nitrogen  in  two 
50  cc.  portions. 

Titrations  (1)  cc.  NH3 

(2)  cc.NH3 

Average , cc.  NH8 

Mg.  N  per  cc.  in  solution  used 

Mg.  N  per  cc.  in  percolate 

Percent  N  fixed  by  soil 

(b)  Repeat  the  experiment,  using  200  gm.  of  the  same  soil. 

Titrations  (1)  cc.  NH3 

(2)  cc.NH3 

Average cc.  NH3 

Mg.  N  per  cc.  in  solution  used 

Mg.  N  per  cc.  in  percolate 

Percent  N  fixed  by  soil 

(c)  Repeat  the  experiment,  using  200  gm.  of  sandy  soil. 

Titrations  (1)   cc.  NH3 

(2)   cc.  NH3 

Average cc.  NH3 

Mg.  N  per  cc.  in  solution  used  ...   

Mg.  N  per  cc.  in  precolate 

Percent  N  fixed  by  soil 

Give  a  general  reaction  for  the  fixation  of  bases  by  soils  and  explain 
fully  what  chemical  elements  that  are  important  in  soil  fertility  may  be 
retained  in  soils  by  means  of  this  reaction. 


16 

PRACTICE  7. 

NITRIFICATION. 

Dilute  20  cc.  of  the  standard  ammonium  sulfate  solution  to  500  cc., 
add.  3  gm.  of  dipotassium  phosphate,  5  gm.  of  calcium  carbonate,  and 
about  2  gm.  of  fresh  rich  garden  soil.  Mix  well,  let  settle,  and  draw  off 
two  loo  cc.  portions. 

Place  500  gm.  of  clean  washed  and  dried  white  sand  in  a  percolator. 
Upon  this  pour  100  cc.  of  the  above  solution  and  immediately  wash  the 
sand  with  about  500  cc.  of  ammonia-free  water,  collect  the  washings  and 
make  up  to  exactly  500  cc.  Place  250  cc.  portions  in  copper  flasks,  add  10 
cc.  of  alkali  and  determine  the  nitrogen  in  the  usual  way.  Compare  the 
amount  of  nitrogen  distilled  as  ammonia  with  that  originally  applied  in 
the  ammonium  sulfate. 

Titrations  (1)   cc.  NH3 

(2)     cc.  NH3 

Average cc.  NH3 

Mg.  N  found 

Add  the  other  100  cc.  portion  of  ammonium  sulfate  solution  to  500 
grams  of  clean,  washed  and  dried  sand  in  a  percolator  and  allow  to  stand 
in  a  dark  place  at  warm  room  temperature  for  four  weeks.  Then  wash 
out  and  determine  the  ammonia  nitrogen  as  directed  above. 

Titrations  (1) cc.  NH3 

(2)   cc.  NH3 

Average cc.  NH8 

Mg.  N  found   

Percent  N  nitrified 

What  change  has  been  brought  about  and  how? 
Explain  fully. 


18 

PRACTICE  8. 

DETERMINATION  OF  NITROGEN  IN  REAGENTS. 

Measure  out  exactly  10  cc.  of  the  concentrated  alkali  in  a  beaker  and 
dilute  to  200  cc.  with  distilled  water.  Stir  and  add  slowly  (finally  drop  by 
drop)  concentrated  sulfuric  acid  until  the  alkali  is  neutralized,  as  shown 
by  the  change  of  color. 

10  cc.  alkali  are  equivalent  to cc.  H2SO4 

How  many  cc.  of  alkali  are  necessary  to  neutralize  20  cc.  H8SO4  ? 

Place  approximately  2  grams  of  pure  sugar  in  a  Kjeldahl  flask,  add  by 
measure  approximately  .650  gm.  metallic  mercury  and  20  cc.  sulfuric  acid. 
Digest  in  a  ventilated  hood  over  a  low  flame  till  colorless,  add  carefully, 
while  still  boiling  hot,  powdered  potassium  permanganate  until  the  solution 
is  green.  Allow  to  cool.  Transfer  with  200  cc.  of  ammonia-free  water  to 
a  copper  flask  by  means  of  a  large  funnel  supported  on  an  iron  ring.  Add 
carefully  sufficient  concentrated  alkali  to  neutralize  20  cc.  of  concentrated 
sulfuric  acid,  connect  with  the  condenser,  shake  until  thoroughly  mixed, 
and  distill  as  usual. 

Titrations  (1)   cc.  NH3 

(2)   cc.  NHa 

Average cc.  NH8 

Check  up  the  standard  ammonia  solution  by  titrating  against  the  stand- 
ard hydrochloric  acid  solution. 

Correction  for  nitrogen  in  reagents  in  terms  of  standard  ammonia  so- 
lution  cc. 

Explain  the  use  of  the  sugar.  Give  the  reaction  between  the  sugar  and 
the  sulfuric  acid.  Why  is  the  mercury  used?  the  potassium  permanganate? 
the  potassium  sulfid? 


20 


PRACTICE  9. 
DETERMINATION  OF  NITROGEN  IN  FARM  PRODUCE. 

Each  group  of  students  will  work  upon  one  of  the  following  materials : 

1.  Wheat  5.  Oats. 

2.  Corn.  6.  Red  Clover  Hay. 

3.  Corn  Stover.  7.  Alfalfa. 

4.  Corn  Cobs.  8.  Oat  Straw. 

Weigh  out  exactly  2  gm.  of  the  material  numbered  with  your  group 
number  and  determine  the  nitrogen  in  it  according  to  the  method  given 
in  the  Eighth  Practice. 

Titrations cc.  NH3 

cc.  NH3    Percent  N 

Average cc.  NH3 

Calculate  the  results  obtained  and  with  these  record  the  results  ob- 
tained by  three  members  of  each  group  as  indicated  upon  the  following 
page,  valuing  nitrogen  at  15  cents  per  pound.  How  many  tons  of  red  clover 
must  be  plowed  under  in  order  to  supply  in  this  way  the  nitrogen  for  a 
loo-bushel  crop  of  corn  and  a  75-bushel  crop  of  oats  in  a  corn,  oats  and 
clover  rotation  ? 

Compute  the  pounds  of  nitrogen  required  to  produce  the  crops  given 
in  the  table  below.  Compute  the  weight  of  sodium  nitrate  (95%  pure), 
which  would  supply  the  nitrogen  found  in  these  crops,  and  the  cost  of  the 
same. 


KIND  OF  PRODUCE 

Pounds 
N  in 
Produce 

Pounds 
NaN03 
equiv. 

Cost 
of 

NaNO3 

(1)    85  bu.  shelled  corn 

(2)     1  200  Ib.  cobs 

(3)    stover,  wt.  equal  to  (1)  -t~  (2) 

(4)     75  bu.  oats 

(5)    4000  Ib.  oat  straw 

(6)     3  tons  clover  hay 

Total  for  three  crops 

PRACTICE  9— (Cont.) 


NAME  OF  STUDENT 

KIND  OF  PRODUCE 

Percent  N 

N  ii 

i  1  ton 

Ib. 

Value 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

22 

PRACTICE  10. 
DETERMINATION  OF  NITROGEN  IN  ANIMAL  EXCREMENTS  :   SOLID  AND  LIQUID. 

Each  group  of  students  will  work  upon  one  of  the  following  : 

1.  Horse  excrements. 

2.  Steer  excrements. 

3.  Cow  excrements. 

4.  Sheep  excrements. 

5.  Swine  excrements. 

6.  Poultry  excrement  and  fresh  cow's  milk. 

7.  Human  excrements. 

8.  Wheat  straw  and  manger  refuse   (for  bedding). 

Record  age  and  condition  of  animals  and  food  rations  as  nearly  as 
possible  in  all  cases. 

For  solid  excrements  :  Weigh  out  10  grams  of  fresh  substance  on  filter 
paper,  placed  on  a  watch-glass,  and  transfer  both  paper  and  excrement  to 
a  Kjeldahl  flask. 

For  liquid  excrement:     Measure  out  10  cc.  and  place  in  a  Kjeldahl 
flask.    Compute  weight  from  specific  gravity  ....................  gm. 

Solid  Liquid. 

Titrations  (1)  ..............  cc.  NH3    Titrations  (1)  ..............  cc.  NH8 

(2)  ..............  cc.NH3  (2)  ............  cc.NH3 

Average  ...................  cc.  NH3    Average  ...............   .  .  cc.  NH3 


Calculate  the  results  obtained  and  with  these  record  the  results  obtained 
by  three  members  of  each  group  as  indicated  upon  the  following  page. 
Value  N  at  15  cents  per  pound. 

10  tons  alfalfa  hay  contain  .........................  Ib.  N 

i  ton  fresh  cow  dung  contains  ......................  Ib.  N 

How  many  tons  of  fresh  cow  dung  would  be  required  to  furnish  nitro- 
gen for  10  tons  of  alfalfa  hay? 


PRACTICE  10.-(Cont.) 


NAME  OF  STUDENT 

Kind  of 
Manure 

Percent  N 

Lb.  N  per  ton  and  value 

Liquid 

Solid 

Liquid 

Value 

Solid 

Value 

Average 

Average 

i 

Average 

Average 



Average 

Average 

Average 

Average 

24 


PRACTICE  ii. 

DETERMINATION  OF  NITROGEN  IN  FERTILIZERS. 

Weigh  out  Yz  gram  of  each  of  the  following  materials  and  use  20  cc. 
of  standard  hydrochloric  acid  in  the  receiver. 

(a)  Ammonium  sulfate. 

(b)  Dried  blood. 

(c)  Sodium  nitrate.     (Use  the  Kjeldahl  method  modified  for  nitrates. 
Mix  2  gm.  salicylic  acid  with  the  sodium  nitrate  in  flask  and  add  30  cc. 
sulfuric  acid.    Use  il/2  times  the  usual  amount  of  alkali  in  the  distillation 
to  neutralize  the  larger  amount  of  sulfuric  acid.) 


Titrations 
cc.  NH3 

Average 
corrected 

cc.  NH  3 
from  sample 

Percent  N 

Value  per  ton 
(N  15c.  perlb.) 

<a)  (1) 

(2) 

(b)  (1) 

(2) 

(c)   (1) 

(2) 

How  would  the  reaction  of  the  soil  be  affected  by  the  residues  left  by 
each  of  these  materials  when  used  to  supply  nitrogen  for  plant  growth? 


26 

PRACTICE  12. 
DETERMINATION  OF  NITROGEN  IN  SOILS. 

Each  group  of  students  will  work  upon  one  of  the  following : 

1.  Surface  of  gray  silt  loam. 

2.  Subsoil  of  gray  silt  loam. 

3.  Surface  of  brown  silt  loam. 

4.  Subsoil  of  brown  silt  loam. 

5.  Surface  of  black  clay  loam. 

6.  Subsoil  of  black  clay  loam. 

7.  Sandy  soil. 

8.  Peaty  soil  (use  5  gm.  soil  and  20  cc.  standard  HC    in  receiver.) 
For  all  soils  except  peat  weigh  out  10  gm.  air-dry  soil  and  use  10  cc. 

of  standard  hydrochloric  acid  in  the  receiver. 

Titrations  (1) cc.  NH3 

(2) , cc.NH3 

Average cc.  NH8 

Percent  N 

Calculate  the  results  obtained  and  with  these  record  the  results  ob- 
tained by  three  members  of  each  group  as  indicated  upon  the  following 
page. 

Assuming  there  are  2,000,000  Ib.  in  an  acre  to  the  depth  of  seven 
inches,  how  many  pounds  of  nitrogen  are  there  in  this  plowed  soil?  How 
many  loo-bushel  crops  of  corn  will  this  produce  if  the  total  crop  is  re- 
moved ? 


PRACTICE  12.— (Cont. 


NAME  OF  STUDENT 

Kind  of    Soil 

Percent 

N 

Pounds  of  N 
Per  Stratum 

No.  of  100-bu. 
Crops  of  Corn 
Equivalent 

AVERAGE 

- 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

28 

PRACTICE  13. 

Determine  nitrogen  in  some  soil  or  other  material  in  which  you  are 
interested,  reporting  to  the  instructor  the  material  decided  upon  before 
undertaking  the  work. 

The  results  of  the  whole  class  shall  be  collected  by  each  man  and  tabu- 
lated as  follows : 


NAME  OF  STUDENT 


Material 


Source 


Percent  N 


30 

PRACTICE  14. 

PREPARATION   OF   STANDARD   SODIUM   HYDROXID   AND   NORMAL   POTASSIUM 
NITRATE  SOLUTIONS.* 

These  solutions  are  to  be  used  in  the  determination  of  soil  acidity. 

(a)  Weigh  out  enough  sodium  hydroxid  (sticks,  purified  over  alcohol, 
about  75  <J0  NaOH)  to  make  3  liters  of  solution  of  such  strength  that  I  cc. 
shall  be  equivalent  to  4  mg.  of  calcium  carbonate.     Dissolve  in  ammonia- 
free  water,  dilute  to  exactly  1000  cc.,  add  100  cc.  of  a  saturated  barium  hy- 
droxid solution,  shake  well,  and  allow  to  stand  over  night,  or  until  clear. 
Draw  off  100  cc.  of  the  clear  solution,  place  in  a  250  cc.  bottle  containing 
100  cc.  of  the  saturated  solution  of  barium  hydroxid.     If  a  precipitate  oc- 
curs, add  the  200  cc.  to  the  main  solution,  shake  and  repeat  the  above  op- 
erations until  no  further  precipitate  occurs.     (If  no  precipitate  is  formed 
throw  away  the  200  cc.)     Always  keep  an  exact  record  of  the  amount  of 
liquid  remaining  in  the  stock  bottle.    When  the  solution  is  free  from  car- 
bon dioxid,  draw  off  100  cc.  and  place  in  a  100  cc.  bottle.    Fill  the  burette 
with  this  and  titrate  against  10  cc.  portions  of  standard  hydrochloric  acid. 
Add  ammonia-free  water  so  that  I  cc.  of  the  standard  sodium  hydroxid 
solution  shall  be  exactly  equivalent  to  4  mg.  of  calcium  carbonate. 

(b)  Prepare  5  liters  of  a  normal  potassium  nitrate  solution,  assuming 
the  salt  to  be  pure. 

If  100  grams  of  an  acid  soil  are  placed  in  250  cc.  of  normal  potassium 
nitrate  solution  and  shaken  for  three  hours  a  reaction  takes  place  between 
the  potassium  nitrate  and  the  acid  constituents  of  the  soil,  giving,  as  one 
of  the  products,  soluble  acid  salts  and  so  making  the  acidity  determinable. 
An  equilibrium  is  reached,  however,  before  this  reaction  runs  to  an  end 
and  if,  after  having  drawn  off  125  cc.  to  titrate,  125  cc.  of  fresh  potassium 
nitrate  are  added  to  the  bottle  and  the  bottle  again  shaken  for  three  hours, 
125  cc.  drawn  off  will  give  a  titration,  which  is  more  than  one-half  of  the 
first.  By  continuing  this  process  until  the  last  125  cc.  shows  practically  no 
acidity,  we  have  a  series  of  titrations  the  sum  of  which  represents  the  total 
acidity  of  the  100  gm.  of  soil.  It  has  been  found  by  working  with  a  num- 
ber of  different  soils  that  as  an  average  the  sum  of  such  a  series  is  2^2 
times  the  first  titration. 

Consequently  when  the  sodium  hydroxid  is  made  up  so  that  i  cc.  is 
equivalent  to  4  mg.  of  calcium  carbonate  and  125  cc.  (which  represents 
50  gm.  of  soil)  are  titrated,  each  o.i  cc.  required  to  neutralize  corresponds 
to  i  mg.  of  calcium  carbonate  required  by  the  100  gm.  of  soil,  or  to  o.ooi 
%  of  calcium  carbonate  required  by  the  soil  tested. 


*To  be  done  by  the  instructor. 


32 

PRACTICE  15. 
DETERMINATION  OF  ACIDITY  (OR  LIME  REQUIREMENT)  OF  SOILS. 

Each  group  of  students  will  work  upon  one  of  a  group  of  soils  selected 
by  the  instructor  using  surface,  sub-surface,  and  subsoil  samples. 

Place  100  gm.  of  soil  in  a  400  cc.  (or  12  oz.)  wide-mouthed  bottle,  add 
250  cc.  normal  potassium  nitrate  solution,  stopper,  and  shake  continuously 
for  three  hours  in  a  shaking-machine,  or  every  five  minutes  by  hand.  Let 
stand  over  night.  Draw  off  125  cc.  of  the  clear  supernatant  liquid,  boil 
10  minutes  to  expel  carbon  dioxid,  cool,  and  titrate  with  the  standard 
sodium  hydroxid,  using  phenolphthalein  as  indicator. 

Surface.    Subsurface.    Subsoil. 

Titrations  (i) cc.  NaOH 

(2)    cc.  NaOH 

Average  cc.  NaOH 

Are  carbonates  present  in  the  soil?    Explain  the  test  for  carbonates. 

Calculate  the  results  obtained  and  with  these  record  the  results  obtained 
by  three  members  of  each  group  as  indicated  on  the  following  page.  Con- 
sider 7  acre-inches  to  weigh  2,000,000  ft). 

What  kind  of  crops,  and  in  what  way,  does  ground  limestone  mainly 
benefit? 


PRACTICE  15— (Cont.) 


NAME 
OF 
STUDENT 

Kind 
of 
Soil 

Percent  CaCOj  required 

Pounds  CaCOj  Required  per  Acre 

Surface 

Subsurface 

Subsoil 

Surface 

Subsurface 

Subsoil 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

33 


34 

PRACTICE  16. 
PREPARATION  OF  PLANT  FOOD  SOLUTIONS.* 

Solution  No.  i. — Nitrogen:  Dissolve  80  gm.  of  ammonium  nitrate  in 
2500  cc.  of  distilled  water.  Use  10  cc.  per  pot. 

Solution  No.  2. — Phosphorus:  Dissolve  25  gm.  of  monocalcium  phos- 
phate in  2500  cc.  of  ammonia-free  water.  Use  10  cc.  per  pot. 

Solution  No.  3. — Potassium:  Dissolve  50  gm.  of  potassium  sulfate  in 
2500  cc.  of  ammonia-free  water.  Use  10  cc.  per  pot. 

Solution  No.  4. — Magnesium :  Dissolve  20  gm.  of  magnesium  sulfate  in 
2500  cc.  of  ammonia-free  water.  Use  10  cc.  per  pot. 

Solution  No.  5. — Iron:  Dissolve  o.i  gm.  ferric  chlorid  in  250  cc.  of 
ammonia-free  water.  Use  I  cc.  per  pot. 

Prepare  these  solutions  carefully,  using  chemically  pure  salts,  and  label 
each  bottle. 


*To  be  done  by  the  instructor. 


36 

PRACTICE  17. 
PREPARATION  OF  POT  CULTURES. 

Use  clean,  white  sifted  sand  in  5-liter  heavy  glass  battery  jars,  having  a 
I  cm.  hole  within  I  cm.  of  the  bottom.  Into  the  hole  fit  a  drain  tube  made 
of  glass-tubing  with  a  glass-wool  filter  at  the  inner  end,  so  that  it  will 
take  liquid  from  the  lowest  place  in  the  jar.  Put  up  a  series  of  ten  of 
these  pots,  eight  to  be  used  as  indicated  in  the  table  below  and  two  in  an 
experiment  to  be  devised  by  the  student.  The  previous  treatment  of  the 
sand  in  the  latter  two  will  depend  upon  the  experiment  to  be  made. 

To  extract  the  sand,  fill  the  jar  within  I  cm.  of  the  top  with  dry  sifted 
sand  and  add  to  this  dilute  sulfuric  acid  (made  by  adding  100  cc.  of  con- 
centrated chemically  pure  sulfuric  acid  to  900  cc.  of  ammonia-free  water) 
until  the  sand  is  saturated.  Let  stand  two  hours  and  then  add  ammonia- 
free  water,  allowing  the  drainage  to  flow  into  a  second  jar  until  it  is  sat- 
urated. Allow  this  jar  to  stand  two  hours  and  then  wash  both  with 
ammonia-free  water  until  free  of  acid.  In  this  way  any  soluble  plant 
food  is  removed  from  the  sand  and  one  portion  of  acid  extracts  two  jars. 
The  sand  for  two  of  the  jars,  in  which  experiments  are  to  be  made  to 
show  the  effect  of  nitrogen-gathering  bacteria,  is  first  heated  to  120°  to 
130°  for  one-half  hour  and  then  extracted  and  washed  as  above. 

Before  planting,  mix  with  the  sand  of  each  pot  10  gm.  of  pure  calcium 
carbonate. 

In  making  applications  of  plant  food  as  indicated  in  the  following  table 
and  in  such  amounts  as  are  shown  in  Practice  16  the  solutions  to  be  ap- 
plied to  each  pot  are  to  be  mixed  together,  and  diluted  to  1000  cc.  Mix 
thoroughly  and  apply  the  whole  amount  to  the  pot,  allowing  any  water 
present  to  be  forced  out  through  the  drain. 

The  first  application  of  the  plant  food  solutions  is  to  be  made  at  the 
time  of  planting,  the  second  three  weeks  later,  the  third  two  weeks  later, 
and  subsequent  applications  at  intervals  of  one  week,  each  time  making 
the  application  as  directed  above. 

Each  student  in  each  group  will  prepare  and  care  for  a  series  of  pots 
as  indicated  in  the  following  table . 


PRACTICE  17.-(Cont.) 


Pot 
No. 

Preparation 
of  sand 

Plant  food 
added 

SEEDS  PLANTED 

Group  1 

2 

3 

4 

5 

6 

7 

8 

'• 

Extract  and  wash 

None 

Corn 

Oats 

Wheat 

Cow 

Peas 

Red 
Clover 

Soy 
Beans 

Rape 

Beets 

2. 
3. 

4. 
5. 
6. 
7. 
8. 

'« 

All  but  N 

.c 

« 

« 

« 

H 

« 

M 

« 

« 

All  but  P 

« 

H 

M 

cc 



« 

All  but  K 

« 

1C 

« 

« 

«' 

M 

None 

All 

(c 

« 

« 

•< 

« 

« 

cc 

" 

None 

All 

Red 
Clover 

Cow 
Peas 

Soy 
Beans 

Vetch 

Alfalfa 

Sweet 
Clover 

Crim- 
son 
Clover 

Alsike 
Clover 

Heat,  extract  and  wash 

All  but  N 

H 

" 



H 

All  but  N 
Bacteria  * 

(( 

« 

« 

« 

H 

1C 

cc 

*Obtain  about  l/£  kilo  of  soil  which  has  recently  grown  the  infected  legume  and 
shake  it  up  with  about  one  liter  of  water.  Let  settle  and  to  each  seed  as  it  is  planted 
add  10  cc.  of  the  supernatant  liquid,  before  the  seed  is  covered. 

Why  is  the  CaCO3  added?  Why  were  two  of  the  pots  heated?  Make  observations 
and  at  least  weekly  notes  of  any  differences  in  growth  and  explain. 


42 

PRACTICE  18. 
PREPARATION  OF  AMMONIUM  MOLYBDATE  SOLUTION.* 

Dissolve  loo  gm.  of  molybic  acid  in  400  cc.  of  ammounium  hydroxid  of 
.96  specific  gravity  and  pour  this  solution  slowly  and  with  constant  stirring 
into  1250  cc.  of  nitric  acid  of  1.20  specific  gravity.  It  is  best  to  cool  the 
acid  after  the  addition  of  each  small  amount  of  ammonium  hydroxid.  Keep 
the  mixture  in  a  warm  place  several  days,  or  until  a  portion  heated  to  4O9 
deposits  no  yellow  precipitate  of  ammonium  phosphomolybdate. 


PRACTICE  19. 
PREPARATION  OF  A  STANDARD  POTASSIUM  HYDROXID  SOLUTION.* 

Dissolve  the  number  of  grams  of  chemically  pure  potassium  hydroxid 
(usually  about  85  %  )  sufficient  to  make  4  liters  of  a  solution,  one  cc.  of 
which  will  be  equivalent  to  .5  mg.  of  phosphorus,  in  400  cc.  distilled  water. 
Remove  carbonates  with  barium  hydroxid,  as  in  Practice  14.  Then  make 
up  to  500  cc.  and  titrate  10  cc.  portions  with  standard  hydrochloric  acid, 
using  phenolphthalein  as  indicator.  Compute  the  exact  weight  of  potas- 
sium hydroxid  in  the  remaining  solution  and  dilute  with  a  sufficient  quan- 
tity of  water  to  reduce  the  strength  to  exactly  2.0809  Sm-  potassium  hy- 
droxid per  100  cc.,  so  that  I  cc.  is  equivalent  to  .5  mg.  phosphorus. 

Mix  well,  check  up  by  again  titrating,  and  label :  Standard  Potassium 
Hydroxid  (ice. — 5  mg.  P.) 


PRACTICE  20. 

PREPARATION  OF  A  STANDARD  NITRIC  ACID  SOLUTION.* 

Determine  the  specific  gravity  of  concentrated  nitric  acid.  Measure  out 
sufficient  to  make  4  liters  of  solution  of  a  strength  equivalent  per  cc.  to  the 
standard  potassium  hydroxid  solution.  Dilute  with  ammonia-free  water 
to  3^2  liters  and  titrate  25  cc.  portions  of  the  standard  potassium  hydroxid 
with  the  dilute  nitric  acid,  using  phenolphthalein  as  indicator.  Then  add 
sufficient  ammonia-free  water  to  make  the  nitric  acid  of  the  same  titrating 
strength  as  the  standard  alkali.  Mix  thoroughly  and  check  up  by  another 
titration. 


*To  be  done  by  the  instructor. 


44 

PRACTICE  21. 
DETERMINATION  OF  TOTAL  PHOSPHORUS  IN  FERTILIZERS. 

Each  group  of  students  will  work  upon  one  of  the  following  materials : 

1.  Bone  Ash.  5.  Raw  Rock  Phosphate. 

2.  Raw  Bone  Meal.  6.  Acidulated  Rock  Phosphate. 

3.  Steamed  Bone  Meal.  7.  Double  Superphosphate. 

4.  Acidulated  Bone  Meal.  8.  Basic  Slag  Phosphate. 

For  materials  containing  more  than  9  percent  of  phosphorus  use  i  gm., 
for  lower  percentages  use  2  gm.  Ignite  in  a  crucible  to  destroy  organic 
matter.  Transfer  to  a  beaker  and  dissolve  in  15  cc.  of  hydrochloric  acid 
(concentrated  hydrochloric  acid  plus  an  equal  volume  of  ammonia-free 
water)  by  the  aid  of  gentle  heat.  Transfer  to  a  250  cc.  measuring  flask, 
cool,  and  dilute  to  exactly  250  cc.  Mix  well,  transfer  to  a  dry  bottle,  and 
let  settle. 

Place  25  cc.  in  a  250  cc.  beaker,  add  5  cc.  of  nitric  acid  (concentrated 
nitric  acid  plus  an  equal  volume  of  ammonia-free  water),  just  neutralize 
with  ammonia,  and  clear  up  with  a  few  drops  of  nitric  acid,  using  heat  if 
necessary  but  avoiding  more  than  a  few  drops  in  excess.  Heat  to  so°-6op 
on  a  water-bath,  add  35  cc.  of  the  clear  molybdate  solution,  stir,  keep  at 
50? -60°  for  two  hours,  let  stand  in  the  desk  over  night.  Filter,  wash  twice 
by  decantation,  using  25  cc.  portions  of  distilled  water,  stirring  thoroughly, 
and  then  allowing  the  precipitate  to  settle  before  decanting  upon  a  9  cm. 
filter.  Transfer  the  precipitate  to  the  filter,  and  wash  the  beaker  and  filter 
seven  or  eight  times  with  small  amounts  of  ammonia-free  water  until  free 
of  acid.  Place  the  filter  containing  the  precipitate  in  the  beaker  and  add 
standard  potassium  hydroxid  in  10  cc.  portions  until  the  precipitate  is  dis- 
solved. Titrate  the  excess  alkali  with  standard  nitric  acid,  using  phenol- 
phthalein  as  an  indicator. 

cc.  HNO8  cc.  KOH  to  mg.  P  % 

used  dissolve  ppt. 


Ave. 


46 

PRACTICE  22. 

PREPARATION  OF  A  NEUTRAL  AMMONIUM  CITRATE  SOLUTION.* 

To  370  grams  of  commercial  citric  acid  add  commercial  ammonia,  spe- 
cific gravity  .96,  until  nearly  neutral;  reduce  the  specific  gravity  to  nearly 
1.09  and  make  exactly  neutral,  testing  as  follows:  Prepare  a  solution  of 
fused  calcium  chlorid,  200  grams  to  the  liter,  and  add  one-fourth  volume 
of  strong  alcohol.  Make  the  mixture  exactly  neutral,  using  a  small  amount 
of  freshly  prepared  corallin  solution  as  a  preliminary  indicator,  and  test 
finally  by  withdrawing  a  portion,  diluting  with  an  equal  volume  of  water, 
and  testing  with  cochineal  solution;  50  cc.  of  this  solution  will  precipi- 
tate the  citric  acid  from  10  cc.  of  the  citrate  solution.  To  10  cc.  of  the 
nearly  neutral  citrate  solution  add  50  cc.  of  the  alcoholic  calcium  chlorid 
solution,  stir  well,  filter  at  once  through  a  folded  filter,  dilute  with  an 
equal  volume  of  water,  and  test  the  reaction  with  a  neutral  solution  of 
cochineal.  If  acid  or  alkaline,  add  ammonia  or  citric  acid,  as  the  case  may 
be,  mix,  and  test  again,  as  before.  Repeat  this  process  until  a  neutral  re- 
action is  obtained.  Add  sufficient  water  to  make  the  specific  gravity  1.09 
at  20°. 


*To  be  done  by  the  instructor. 


48 

PRACTICE  23. 
DETERMINATION  OF  CITRATE-INSOLUBLE  PHOSPHORUS. 

Use  the  same  amounts  and  materials  as  in  Practice  21.  If  the  material 
is  acid,  wash  the  weighed  sample  on  a  9  cm.  filter  with  water  until  free 
of  acid. 

Heat  in  a  water-bath  100  cc.  of  the  neutral  ammonium  citrate  solution 
to  65°  in  a  200  cc.  Erlenmeyer  flask,  loosely  stoppered  with  a  stopper  hold- 
ing a  ioo°-  thermometer.  When  6sp  is  reached  put  in  the  sample  and  shake 
thoroughly.  Place  in  the  bath  at  65°  and  let  stand  for  30  minutes,  shaking 
every  five  minutes.  At  the  end  of  30  minutes  filter  and  wash  thoroughly 
with  water  at  65°  until  all  soluble  phosphorus  is  removed  (test  for  soluble 
phosphorus  with  I  cc.  of  ammonium  molybdate  solution).  Transfer  the 
filter  and  its  contents  to  a  crucible,  dry,  and  then  ignite  until  all  organic 
matter  is  destroyed,  transfer  to  a  beaker,  add  about  15  cc.  of  hydrochloric 
acid,  and  heat  until  all  phosphorus  is  dissolved.  Make  up  to  250  cc.,  mix 
well,  transfer  to  a  dry  bottle,  and  let  settle.  Determine  phosphorus  in  25 
cc.  portions  according  to  the  directions  given  in  Practice  21. 

cc.  HNO3  cc.  KOH  to  mg.  P  %P 

used  dissolve  ppt. 


Ave 

Calculate  the  results  obtained  in  Practices  21  and  23  and  with  these 
record  the  results  obtained  by  three  members  of  each  group  as  indicated 
in  the  table  on  the  following  page.  Value  citrate-soluble  phosphorus  at  12 
cents  and  insoluble  phosphorus  at  5  cents  a  pound. 


PRACTICE  23. -(Con't.) 


NAME  OF  STUDENT 

Material 

Citrate 
Soluble 
Percent 

Insoluble 
Percent 

Total 
Percent 

Value  per 
Ton 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

*                                   AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

49 


50 

PRACTICE  24. 
DETERMINATION  OF  PHOSPHORUS  IN  FARM  PRODUCE. 

Each  group  of  students  will  work  upon  one  of  the  following  products : 

1.  Wheat.  5.  Oats. 

2.  Corn.  6.  Oat  Straw. 

3.  Corn  Stover.  7.  Red  Clover  Hay. 

4.  Corn  Cobs.  8.  Alfalfa  Hay. 

Weigh  out  2  gm.  of  the  material  in  a  25  cc.  crucible,  moisten  with  a 
?o%  solution  of  ammonium  nitrate,  and  ignite  in  a  muffle  furnace  at  a 
low  red  heat  for  two  hours.  Transfer  to  a  250  cc.  beaker,  dissolve  in  about 
15  cc.  of  hydrochloric  acid,  dilute  to  about  40  cc.,  filter  and  wash.  Evap- 
orate the  filtrate  and  washings  to  about  25  cc.  and  determine  phosphorus 
according  to  directions  given  in  Practice  21,  using  only  10  cc.  of  the  am- 
monium molybdate  solution. 

cc.  HNO3  cc.  KOH  to  mg.  P  #P 

used  dissolve  ppt. 


Ave .... 

Calculate  the  results  obtained  and  record  with  these  the  results  ob- 
tained by  three  members  of  each  group  as  indicated  on  the  following  page. 
Value  phosphorus  at  12  cents  per  pound. 

How  many  pounds  of  steamed  bone  meal  will  it  require  to  replace  the 
phosphorus  removed  from  the  soil  in  a  loo-bushel  crop  of  corn,  a  75- 
bushel  crop  of  oats,  and  a  3-ton  crop  of  clover  hay  (see  Practice  9)  ? 


PRACTICE  24  (Cont.) 


NAME  OF  STUDENT 

Material 

Percent  P 

Pounds  P 
Per  Ton 

Value 
Per  Ton 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

51 


52 

PRACTICE  25. 
FIXATION  OF  PHOSPHORUS  BY  SOILS. 

Each  group  of  students  will  use  one  of  the  following  soils : 

1.  Surface  of  gray  silt  loam.  5.  Surface  of  black  clay  loam. 

2.  Subsoil  of  gray  silt  loam.  6.  Subsoil  of  black  clay  loam. 

3.  Surface  of  brown  silt  loam.  7.  Sandy  soil. 

4.  Subsoil  of  brown  silt  loam.  8.  Peaty  soil. 

Dissolve  i  gm.  of  double  superphosphate  in  500  cc.  of  water.  Filter 
and  keep  in  a  stoppered  bottle. 

(a)  Determine  the  phosphorus  in  50  cc.  portions  of  this  solution  by 
concentrating  to  25  cc.  and  following  the  directions  given  in  Practice  21. 

cc.  HNO3  cc.  KOH  to  mg.  P  %¥ 

used  dissolve  ppt. 


Ave .... 

(b)  Dilute  50  cc.  of  the  double  superphosphate  solution  to  250  cc.  and 
percolate  through  100  gm.  of  soil  held  in  a  percolator  as  in  Practice  6.  De- 
termine the  phosphorus  in  100  cc.  portions  by  concentrating  to  25  cc.  and 
following  the  directions  given  in  Practice  21,  using  only  15  cc.  of  the  am- 
monium molybdate  solution. 

cc.  HNO3  cc.  KOH  to  mg.  P  f0P 

used  dissolve  ppt. 


Ave 

Percent  phosphorus  fixed  by  soil 

(c)  Thoroughly  mix  10  gm.  of  CaCO3  with  100  gm.  of  the  same  soil, 
dilute  50  cc.  of  the  double  superphosphate  solution  to  250  cc.,  percolate 
through  soil  and  determine  the  phosphorus  in  100  cc.  portions  of  the  per- 
colate in  the  same  manner  as  above. 

cc.  HNO3  cc.  KOH  to  mg.  P  %P 

used  dissolve  ppt. 


Ave ......  

Percent  phosphorus  fixed  by  soil 

Calculate  the  results  obtained  and  with  these  record  the  results  ob- 
tained by  three  members  of  each  group  as  indicated  in  the  table  on  the 
following  page. 

Give  the  general  reaction.  Explain  the  effect  of  the  CaCO3.  How  was 
the  fixation  brought  about  in  the  non-calcareous  soils? 


PRACTICE  25.— (Con't.) 


NAME  OF  STUDENT 

Kind  of  Soil 

Percent  P  Fixed  by 
Soil 

Percent  P  Fixed  by 
Soil  and  Lime 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

AVERAGE 

53 


54 

PRACTICE  26. 
DETERMINATION  OF  PLANT  FOOD  IN  SOILS. 

Each  student  will  select  a  soil  in  which  he  is  especially  interested. 

(a)  Nitrogen. 

Determine  according  to  directions  given  in  Practice  12. 

(b)  .Dry  Matter. 

Weigh  out  5  gm.  of  the  air-dried  soil  in  a  small  porcelain  dish,  dry  at 
100°  for  5  hours,  cool  in  a  desiccator,  and  weigh. 

Weight  of  vessel  plus  dry  matter  

Weight  of  vessel  

Weight  of  dry  matter  

Percent  dry  matter  

Average  

(c)  Insoluble  matter. 

Place  10  gm.  of  the  air-dried  soil  in  a  200  cc.  Erlenmeyer  flask,  add 
100  cc.  of  hydrochloric  acid  (sp.  gr.  1.115),  close  with  a  rubber  stopper  in 
which  is  a  glass  tube  18  inches  long,  and  digest  for  ten  hours  on  the  water- 
bath,  at  the  temperature  of  boiling  water,  shaking  once  every  hour.  Dilute, 
filter  through  a  15  cm.  filter,  wash  free  of  chlorids  with  distilled  water, 
and  evaporate  the  filtrate  and  washings  to  dryness  with  5  cc.  of  nitric  acid 
to  destroy  organic  matter.  Take  up  with  about  10  cc.  of  hydrochloric  acid 
and  about  25  cc.  of  water,  again  run  to  dryness  and  heat  three  hours  in  an 
air-oven  at  110°.  Add  about  15  cc.  of  hydrochloric  acid,  heat  30  minutes 
on  the  water-bath,  dilute,  filter  through  a  9  cm.  filter  and  wash  with  dis- 
tilled water.  Ignite  the  filter  and  contents  with  the  main  portion  of  the 
insoluble  matter. 

Weight  of  crucible  plus  insoluble  matter         

Weight  of  crucible  

Weight  of  insoluble  matter  

Percent  of  insoluble  matter  

Average  

Make  the  filtrate  and  washings  up  to  exactly  500  cc.,  mix  thoroughly 
and  put  in  dry  stoppered  bottle.  Label  it  Solution  A. 

(d)  Phosphorus. 

Evaporate  200  cc.  of  Solution  A  to  about  20  cc.  and  determine  phospho- 
rus according  to  the  directions  given  in  Practice  21,  using  15  cc.  of  the 
clear  ammonium  molybdate  solution. 

cc.  HN03  cc.  KOH  to  mg.  P  #P 

used  dissolve  ppt. 


Ave 

(e)  Potassium,  Sodium,  and  Iron. 

Evaporate  100  cc.  of  Solution  A  to  complete  dryness.  Add  about  25 
cc.  of  hot  water  and  50  cc.  of  a  saturated  barium  hydroxid  solution,  let 
stand  30  minutes  on  the  water-bath,  filter  through  an  n  cm.  filter,  and 


56 

PRACTICE  26.— (Con't) 

wash  with  hot  water  until  free  of  chlorids.  Dissolve  the  precipitate  from 
the  filter  with  as  small  an  amount  as  possible  of  warm  dilute  sulfuric  acid 
(i  to  6),  catch  the  solution  and  washings  in  a  200  cc.  Erlenmeyer  flask  and 
treat  this  solution  as  directed  below  for  the  determination  of  iron. 

Concentrate  the  filtrate  from  the  barium  hydroxid  precipitation  to  about 
50  cc.,  add  a  few  drops  of  ammonium  hydroxid  and  10  cc.  of  ammonium 
carbonate  solution,  let  stand  30  minutes  on  the  water-bath,  filter  through 
an  ii  cm.  filter  into  a  10  cm.  evaporating  dish,  and  wash  with  hot  water 
until  free  of  chlorids.  Evaporate  the  filtrate  to  dryness  and  carefully  ig- 
nite the  dish  over  a  Bunsen  burner  to  expel  ammonium  salts.  Take  up 
with  about  10  cc.  of  hot  water,  add  a  few  drops  of  ammonium  hydroxid 
and  ammonium  carbonate,  filter  through  a  9  cm.  filter  into  a  250  cc. 
beaker,  and  wash  with  hot  water.  Concentrate  to  about  25  cc.,  add  5  cc. 
of  ammonium  sulfate  solution  (75  gm.  per  liter),  digest  on  a  water-bath  2 
hours,  and  filter  into  a  250  cc.  beaker  through  a  9  cm.  filter.  Transfer  to  a 
small  weighed  evaporating  dish  or  large  crucible,  and  evaporate  to  dryness. 
Ignite  over  a  Bunsen  burner  to  remove  ammonium  salts.  Add  I  gm.  of 
powdered  ammonium  carbonate,  heat  to  full  redness,  cool  in  a  desiccator, 
and  weigh. 

Weight  of  dish  plus  K2SO4  and  Na2SO4     

Weight  of  dish  

Weight  of  K88O4  and  Na2804  

Weight  of  K..SO4  (computed)  

Weight  of  Na2SO4  

Weight  of  Na  

Percent  Na  

Average  

Take  up  with  a  little  hot  water,  add  a  few  drops  of  hydrochloric  acid 
and  platinic  chlorid  solution  (10  cc.  contain  I  gm.  platinum),  using  .1  cc.  of 
the  platinum  solution  for  every  5  mg.  of  sulfates  found,  evaporate  to  a 
thick  syrup,  wash  seven  times  with  4  cc.  of  80%  alcohol,  decanting  each 
time  through  a  9  cm.  filter,  let  the  filter  dry  thoroughly  at  room  tempera- 
ture, and  dissolve  any  of  the  potassium  platinic  chlorid  on  the  filter  with 
hot  water,  catching  the  solution  in  the  dish  containing  the  greater  part  of 
the  salt,  evaporate  to  dryness,  heat  30  minutes  at  IIOQ  in  an  air-bath,  cool 
in  the  desiccator,  and  weigh. 

Weight  of  dish  plus  KaPtCl6  

Weight  of  dish  

Weight  of  K2PtCl6  

Weight  of  K  

Percent  of  K 

Average  

To  the  200  cc.  Erlenmeyer  flask,  containing  the  iron  in  sulfuric  acid 
solution,  add  i  gm.  of  zinc  dust,  stopper  with  a  cork  carrying  a  delivery- 
tube  bent  so  as  to  dip  into  a  beaker  of  distilled  water.  Let  stand  over 
night  and  titrate  the  reduced  iron  with  potassium  permanganate.  (Solu- 


58 
PRACTICE  26.—  (Con't.) 

tion  to  be  made  by  the  instructor  so  that   i   cc.   shall  be  equivalent  to 
2  mg.  of  iron). 

cc.  KMnO4  used  

Percent  Fe  

Average  

(f)  Aluminum. 

Heat  to  boiling  100  cc.  of  Solution  A  in  a  250  cc.  beaker,  add  ammo- 
nium hydroxid  carefully,  until  an  odor  of  ammonia  is  distinguishable  after 
blowing  into  the  beaker,  let  settle,  and  decant  supernatant  liquid  through 
an  ii  cm.  filter.  Wash  with  about  50  cc.  of  hot  water  by  decantation,  dis- 
solve in  hydrochloric  acid,  dilute  to  100  cc.,  heat  to  boiling,  and  again  pre- 
cipitate by  adding  ammonium  hydroxid  as  above.  Decant  through  the 
same  filter,  transfer  to  the  filter,  and  wash  with  hot  water  until  free  of  chlo- 
rids.  Dry  and  ignite  in  a  weighed  crucible  over  a  Bunsen  burner. 

Weight  of  crucible  plus  A12O3,  Fe2O3,  P2O5 

Weight  of  crucible  

Weight  of  A12O3,  Fe2O8,  P2O6  

Weight  Fe2O3  and  P2O 5  (computed)  

Weight  of  A12O3  

Weight  Al 

Percent  Al  

Average  

(g)  Calcium, 

Concentrate  the  filtrate  from  (f)  to  50  cc.,  add  a  few  drops  of  ammo- 
nium hydroxid  and  then  ammonium  oxalate  until  all  the  calcium  is  pre- 
cipitated. 

Digest  on  the  water-bath  2  hours,  filter  through  a  9  cm.  filter,  wash 
with  hot  water  until  free  of  chlorids,  dry,  and  ignite  in  a  weighed  crucible 
over  a  Bunsen  burner,  finishing  to  constant  weight  over  the  blast  lamp. 

Weight  of  crucible  plus  CaO  

Weight  of  crucible  

Weight  of  CaO  

Weight  of  Ca  

Percent  Ca  

Average  %  

(h)  Magnesium. 

Concentrate  the  filtrate  from  (g)  to  50  cc.,  cool,  add  a  few  drops  of 
ammonium  hydroxid,  then  add  slowly  while  stirring  disodium  phosphate 
solution  until  the  magnesium  is  all  precipitated,  add  10  cc.  of  ammonium 
hydroxid,  cover,  and  let  stand  over  night.  Filter  through  a  9  cm.  filter, 
wash  with  dilute  ammonium  hydroxid  (l  liter  of  ammonium  hydroxid  of 
.96  sp.  gr.  diluted  to  5  liters),  dry,  and  ignite  in  a  weighed  crucible  over  a 
Bunsen  burner,  finishing  to  constant  weight  over  the  blast  lamp. 


60 

PRACTICE  26.— (Con't.) 


Weight  of  crucible  plus  Mg2P207 

Weight  of  crucible 

Weight  of  Mg2P2O7 

Weight  of  Mg 

Percent  Mg 

Average 


PERCENTAGE  COMPOSITION  OF  SOIL. 

Air-dry  Basis.        Dry  Basis. 

Nitrogen  

Phosphorus  

Potassium  

Calcium  

Magnesium  

Iron  

Aluminum  

Sodium  

Insoluble  Matter  

Undetermined  "> 
C,H,O,  etc.       j 

Are  carbonates  present  in  the  soil? 

If  the  soil  is  acid,  what  percent  of  calcium  carbonate  is  required  to  cor- 
rect the  acidity  ? 

Suggest  a  practical  method  of  treatment,  of  unlimited  application,  by 
which  the  productive  capacity  of  this  soil  could  be  profitably  increased  and 
permanently  maintained. 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN  INITIAL  FINE  OF  25  CENTS 

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THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
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NOV  2ft  tQ4fl{\ 

*:*  gt*  <. 

•    f    . 

-  r-q*} 

FEB  1  9  1942 

rCD    JLC7  HBrf* 

LD  21-100m-7,'40  (6936s) 

YC  65758 


O 

s 


CO 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


